Composite doctor blades

Abstract

A composite doctor blade is provided that is suitable for use in the manufacture of paper, particularly for use in calenders. The composite doctor blade includes multiple layers of composite material in which a substantial proportion of the fibers are aligned in a direction substantially parallel to the long axis of the doctor blade.

What is claimed is:  
     
       1. A doctor blade having a long axis for application against a circumferential surface of a roll rotating upon a rotational axis, comprising a composite material comprising a plurality of abrasive unidirectional fibers, aligned in a direction parallel to the long axis of the doctor blade and impregnated with a resin, wherein the unidirectional fibers are provided in a unidirectional fabric that includes, based on fabric weight, at least 60% by weight unidirectional fibers. 
     
     
       2. The doctor blade of  claim 1  wherein the doctor blade has a laminate structure comprising multiple layers of said composite material. 
     
     
       3. The doctor blade of  claim 1  wherein the unidirectional fibers are selected from the group consisting of fiberglass, ceramic, and mixtures thereof. 
     
     
       4. The doctor blade of  claim 3  wherein the unidirectional fibers comprise fiberglass. 
     
     
       5. The doctor blade of  claim 1  wherein the unidirectional fibers comprise long continuous fibers. 
     
     
       6. The doctor blade of  claim 1  wherein at least 75% by weight of the unidirectional fabric comprises unidirectional fibers. 
     
     
       7. The doctor blade of  claim 6  wherein at least 90% by weight of the unidirectional fabric comprises unidirectional fibers. 
     
     
       8. The doctor blade of  claim 1  wherein the unidirectional fabric further comprises secondary fibers. 
     
     
       9. The doctor blade of  claim 8  wherein the unidirectional fibers have diameters equal to or greater than the diameters of the secondary fibers. 
     
     
       10. The doctor blade of  claim 9  wherein the diameters of the unidirectional fibers are about 450 to 1500 μm and the diameters of the secondary fibers are about 400 to 700 μm. 
     
     
       11. The doctor blade of  claim 1  wherein the unidirectional fabric further comprises nonabrasive fibers. 
     
     
       12. The doctor blade of  claim 11  wherein the nonabrasive fibers are selected from the group consisting of carbon, rayon, aramid, polyester, and mixtures thereof. 
     
     
       13. The doctor blade of  claim 12  wherein the nonabrasive fibers comprise carbon fibers aligned in a direction substantially perpendicular to the long axis of the doctor blade. 
     
     
       14. The doctor blade of  claim 1  wherein the unidirectional fabric has a weight per unit area of about 230 to 610 g/m 2 . 
     
     
       15. The doctor blade of  claim 1  wherein the resin comprises a thermoplastic resin. 
     
     
       16. The doctor blade of  claim 1  wherein the resin comprises an epoxy resin. 
     
     
       17. The doctor blade of  claim 1  wherein the resin has a glass transition temperature of about 65 to 315° C. 
     
     
       18. The doctor blade of  claim 17  wherein the resin has a glass transition temperature of about 85 to 315 °C. 
     
     
       19. The doctor blade of  claim 1  wherein the resin further comprises an abrasive additive selected from the group consisting of glass microspheres, glass fibers, crushed glass, synthetic or industrial diamond particles, silica particles, silicon carbide particles, boron particles, zirconium particles, aluminum oxide particles and mixtures thereof.